(1) Field of the Invention
The present invention relates to a method and apparatus for determining the chemical structure of an unknown substance by analysis of the spectral data of the unknown substance obtained from an analysis apparatus, particularly a C-13 nuclear magnetic resonance (below, C-13 NMR) apparatus.
(2) Description of the Prior Art
Up until now, analysis of the structure of an unknown substance has been effected using spectral data by the manual labor and intellectual, mental work of spectroscopists based on their personal experience and spectroscopic theory. This analysis work involves the comparison of the standard spectra of many amount of known substances, judging which features the unknown substance has in common with the spectra of the known substances, and thus deducing the composite elements of the molecular structure, i.e., the partial structures. This takes time and requires considerable experience in data analysis.
Recently, in the field of chemical structural analysis, the same procedures formerly carried out manually by human operators are being performed by computerized data searches, whereby up to tens of thousands of sets of standard spectral data of known substances are compared with the spectral data of the unknown substance so as to determine the chemical structure of the unknown substance.
However, in this conventional method, it is possible to identify an unknown substance as a known substance only when the standard spectral data of the known substance and the spectral data of the unknown substance are a perfect match. Consequently, there is a disadvantage in that no information can be obtained on an unknown substance having a spectrum not included in the standard spectral data. In other words, this conventional method unconditionally considers the position and intensity of the spectral signals in the standard spectral data of the known substances and the spectrum of the unknown substance as specific values and requires complete correspondence of the spectral signals as a condition for identification. Therefore, there is a shortcoming in that a difference in electron density due to a slight difference in molecular structure or a deviation in the numerical value due to an error in measurement makes identification of even a known substance impossible.
Further, up until now, the spectral data of known substances accumulated for C-13 NMR apparatuses covers only approximately 35,000 compounds--even with the most popular collection of standard spectral data compiled by the Satler Co. Almost no data on compounds being daily synthesized for the purpose of development and research of industrial products is contained therein, and for this reason, it is almost impossible, in particular, to determine the chemical structure of byproducts, etc. of synthetic reactions using the conventional method relying on a data search.